In Space, Infectious Diseases Reveal Their True Nature

It turns out that microgravity might reveal a thing or two about the nasty bacteria

When you think about what’s going on hundreds of miles above the surface of the Earth at the International Space Station, you probably don’t think about salmonella. But it turns out that microgravity might reveal a thing or two about the nasty bacteria. Researcher Cheryl Nickerson took some salmonella up there to see what might happen, and what she found was quite surprising. Arizona State University writes:

During an earlier series of NASA space shuttle and ground-based experiments, Nickerson and her team made a startling discovery. Spaceflight culture increased the disease-causing potential (virulence) of the foodborne pathogen Salmonella, yet many of the genes known to be important for its virulence were not turned on and off as expected when this organism is grown on Earth. Understanding how this switching is regulated may be useful for designing targeted strategies to prevent infection.

In fact, the first time they brought salmonella to space and then came down, it returned three to seven times more virulent than the bug grown on the ground. NASA writes:

“We think space travel tricks Salmonella into behaving as if it is in the human gut,” Nickerson says. “It’s a mechanical phenomenon having to do with ‘fluid shear.’”

Basically, when salmonella move around, they can sense how strong the force of the fluid moving past them is. In the small intestine and stomach, that fluid is moving quickly. But if the salmonella can find its way to an alcove, a little nook in the wall of the intestine, that fluid shear goes way down. The salmonella can sense the change and picks that time to bloom. In space, fluid shear is extremely low. So the salmonella think they’re in their safe zone.

This fluid shear has all sorts of important functions to the cell, writes NASA:

As it turns out, many of the genes activated by the low fluid shear environment of spaceflight are involved in transporting these ions in and out of the cells, so there could be a connection. Research on this ion effect is still ongoing, Nickerson says, but she speculates that it could eventually lead to new ways to use these ions to ward off Salmonella infections.

And understanding those genes activated by the shear, or otherwise, could help researchers figure out how to combat the bug here on Earth. Space.com writes:

“This research opens up new areas for investigations that may improve food treatment, develop new therapies and vaccines to combat food poisoning in humans here on Earth, and protect astronauts on orbit from infectious disease,” said Julie Robinson, program scientist for the International Space Station at NASA’s Johnson Space Center in Houston.

Which is a good thing, because salmonella infects something like 40,000 people every year in the United States alone.

In a recent spaceflight experiment aboard space shuttle mission STS-135, the team flew a genetically modified Salmonella-based anti-pneumoccal vaccine that was developed in the Curtiss lab. By understanding the effect of microgravity culture on the gene expression and immunogenicity of the vaccine strain, their goal is to genetically modify the strain back on Earth to enhance its ability to confer a protective immune response against pneumococcal pneumonia.

“Recognizing that the spaceflight environment imparts a unique signal capable of modifying Salmonella virulence, we will use this same principle in an effort to enhance the protective immune response of the recombinant attenuated Salmonella vaccine strain,” Nickerson says.

And later this year, Nickerson will be taking her salmonella to a new ship—the SpaceX Dragon. She’s going to infect a nematode with salmonella on the ship, marking the first time something has been intentionally infected with a pathogen in microgravity. Let’s just hope that none of the astronauts get infected as well, because salmonella in space doesn’t sound so fun.

About Rose Eveleth

Rose Eveleth is a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.